


Monster, How Should I Feel?

by Waifuu



Category: Undertale (Video Game)
Genre: But Not In The Weird Way, F/F, F/M, Fluff, Frisk is not mute, Gaster Being Gaster, Getting Sucked Into The Hole of Sin, I Think I like It, It's a surprise - Freeform, Magical!Reader, MonsterHybrid!Reader, Reader Could End Up With Either, Reader Is Not Frisk, Reader Loves Her Dad, Reader-Insert, Sans Being Sans, Slow Burn, Ugh Tags Tho, like way later, maybe smut
Language: English
Status: In-Progress
Published: 2016-04-04
Updated: 2016-04-13
Packaged: 2018-05-29 18:34:41
Rating: Teen And Up Audiences
Warnings: Major Character Death
Chapters: 2
Words: 3,037
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6388117
Author URL: https://archiveofourown.org/users/Waifuu/pseuds/Waifuu
Summary: <blockquote class="userstuff">
              <p>You were born in the Underground, and life was pretty good until Chara and Asriel died. After the King had declared war on humanity and proclaimed he would kill any human that falls to the Underground, your father began to act strangely, even going as far as to set up a protective barrier around your home along with a cloaking spell. Although he aided monsters in the war before they were sealed underground and after, the King made no exceptions. Instead of killing him however, he forced him to help W. D. Gaster with his experiments to free monster kind, leaving you on your own until he could return. Unfortunately, he never did.</p><p> With unwavering perseverance, you vowed you would find your beloved father again no matter what the cost. Although the presence of a human child, their cohorts, and their antics certainly made it harder to focus.</p>
            </blockquote>





	1. A Shot In The Dark

**Notes for the Chapter:**

> Hey, friends! I've been obsessed with Undertale for so long and I think I finally got an interesting plot to write! I'll try to be diligent and update this at least once a week! This is my first fic in awhile though and this chapter went through a bunch of redos until I finally felt it was ready. Anyways! I hope you all enjoy! ;u;

Your eyes met with darkness as you opened them gingerly, your body floating gently along in the vast nothingness. A howling wind echoed in all directions, yet your hair and clothes remained untouched. Immediately, you began to flail and shriek in terror. What was going on!? Where were you!? In your panicked fit, you accidentally brought out your soul, a bright light amid the darkness. Reflexively, your arms shot up to shield your eyes as you cried out in surprise. You felt an odd emptiness in your chest and you slowly put down your arms, realizing your soul was the source of the light. An upside down, lavender heart floated a ways away from you, emitting a white light. Gasping in shock, you reached out towards your soul, attempting to bring it back into your chest. Suddenly, a voice pierced through the perpetual wind, its sound causing goosebumps to erupt on your arms as you shivered.

**XXXXX? XXXXXXX…!**

White, skeletal hands with a large hole punctured in the palms suddenly appeared near your soul, hovering on either side, and stopping you from bringing it back. You ignored them, instead staring at the looming figure the hands were seemingly attached to. Trembling in fear, you stared up at a pale, grinning face whose eyes lingered on your soul. A black crack was underneath one eye socket while a second was above the other droopier one. It wore what seemed to be a grey turtleneck sweater and black labcoat, but both had fused together along with the rest of its body below its breast, where its black gooey mass appeared to melt and reform constantly. The entity kept speaking to you, but you couldn’t understand its unnerving, warbled language. You wanted to scream, to cry, to say something! Anything! But you were frozen in terror, waiting with baited breath for this creature to make its move.

**XXXXXX…XXXX…..**

Finally, it tore its eyes away from your soul to look at your face and it jumped in surprise, recoiling away from you as if it was burned. You both stared at each other in a stunned silence before it tentatively reached its hand out, towards your soul, and panic washed over you tenfold. Suddenly, your soul flew back into your chest and your body was violently yanked from behind, away from the strange entity.

 

You awoke with a start, body sticky with your sweat and heart racing. Frantically, you looked around, half expecting to see the entity hovering about. When you found nothing but your empty room, you calmed down, sighing in relief. That had been rather frightening. You've had nightmares before but none had been quite like that. Wiping sweat from your brow, you swung your legs over the side of your bed and stood. You flicked your finger upward, your ears picking up the subtle clicking of a switch, and the room was suddenly bathed in light. There was no way you could go back to sleep now. Time for a fresh cup of coffee and a good book to distract you from that bad dream.

 

As the day wore on you found your mind wandering back to the dream multiple times. It wasn't like you meant to! It just sort of...happened. You'd go over all the vivid details, trying to determine where exactly you had ended up (though you had a sneaking suspicion it wasn't in the Underground), who and what that creature was that you encountered, and why you were contemplating about going back. Remembering how shocked and horrified you had been didn't seem to squash that longing. You groaned loudly, shutting your spell tome and releasing your magic, several objects then clattering to the floor at once. Getting up from the wooden floor of your home, you rushed to the library, eyes scanning the book cluttered room until they landed on your father's chest. Kneeling in front of it, you flipped the two latches up and lifted the top. You sighed solemnly, heavy sorrow tugging at your heart as you gazed at your father's belongings. He left when you were just a child, right after your mother had succumbed to an awful illness. Out of anger and confusion, you thought that was the reason he left, that you looked so much like her that it caused him an insurmountable amount of pain to be near you. But you knew, in your heart, that that couldn't have been the case. He told you he loved you before he walked out the door, and his last few words to you were words of warning.

_Stay inside this house, . Until you can properly cloak yourself and protect yourself....do not leave. It's imperative that monsters forget you, that none of them know of your existence._

You remembered sobbing hysterically, asking him why. He had cupped your cheeks gently, and pulled you into a hug.

_Because they will kill you.They will kill you and take your soul. You're the only thing left in this world that I cherish...please. Please listen, won't you? I love you, . Daddy... has something important to do...but...but I'll be back okay?_

He never came back.

Sniffling, you wiped the stray tears off your cheeks, banishing the memories away for now as you reached into the chest and retrieved an old worn journal. In it, was everything your father knew about the Void. That he managed to write down anyways.  You leafed through the pages before something had caught your eye. 

_"It must be a glitch...an accident perhaps? Although it was in a dream....everything I saw...felt real. I remember how dark it was there...darker than darkness I would say. The wind that howled was thunderous, yet it did not disturb a single hair  atop my head. I cannot seem to recall how long I floated there aimlessly before I was pulled back to the waking world. I was there. In the Void. Through more trips I realized that only a fragment of me was actually there. Of course, these trips would take a toll on my body. I'd wake up with horrendous migraines, physical aches and pains, as if my lifeforce was slowly draining away. This time I stayed for far too long. I woke up coughing blood and incredibly tired. As if my time wasn't already limited...I need to find him. To save him. It's the least I can do."_

You furrowed your brows. Darker than darkness is how you would have described it... along with the wind. Flipping through more pages with trepidation, the information confirmed your suspicions. But you didn't understand why and how you had managed to appear in the Void. You were far from powerful, only knowing a handful of magic, and you had no connections to the Void. A pale, cracked, face suddenly appeared on a page, freezing you in your tracks. That was the creature you saw in your dream! With shaky fingers, you traced over the drawing in your father's journal, your eyes taking in the words on the page.

_"I found him, thank the stars! But he....Gaster....he's not the same. The accident has wounded him. I need to find a way-"_

You shut the journal. 

Gaster. That's who that entity was. He didn't belong in the Void, he belonged here in the Underground. You didn't know exactly how he got there but you knew your father had been trying to get him out. You had to know why. You had to go back. You had to find out what happened to your father.

 


	2. The Least You Can Do

**Notes for the Chapter:**

> Sorry for the short chapter ;3; I feel like I had to explain a few more things before I really got into the story. Feel free to tell me things I could improve on, I would love to develop my writing for the better! Enjoy!

 

It took quite a few days of trying for you to re-enter the Void. Of course, returning was easier said than done, especially since your first visit was an accident. But, when at last sleep had taken you in its grasp and the howling of wind suddenly thundered all around you, you were more relieved than anything else.

“Finally.”

 Opening your eyes, you looked around in the darkness, willing your body to float forwards. This should be the easy part, shouldn’t it? After all, you wouldn’t be here if someone didn’t want you to be. (Or at least that’s what it said in your father’s journal) Anxiety reared its ugly head as moments became minutes and Gaster was still nowhere to be found. What if Gaster isn’t the one you find? What if the Void was so enormous that it would take you days to find him? How were you going to go back? How would you wake up?

 

**XXXXXXXXX!**

 

A skin crawling, warbled voice pulled you away from your fear induced thoughts and you blinked twice before looking up. Relief once again washed over you as your eyes swept across a pale, cracked face with an unnerving grin. His skeletal hands fidgeted a little before moving towards your face, but out of reflex, you flinched backwards, catching the slight downturn of his grin as he retracted his hands.

You coughed awkwardly into your fist and smiled up at him reassuringly. “U-uhm! I’m going to go ahead and guess that you must be Doctor Gaster?” It never hurt being sure.

It seemed like he was about to speak before he stopped himself and merely tilted his head in affirmation. Content with his answer, you felt yourself relax a bit.

“That’s a relief!” Time to get some answers. “So, I know we got off on the wrong foot and I’m really sorry though honestly it was awfully terrifying ending up here and holy shit you were probably here for so long you must really hate it here and-“

You stopped yourself abruptly as you realized you weren’t as relaxed as you thought you were and had regressed to your nervous habit; rambling. Feeling heat bloom across your cheeks, you glanced up at the doctor, his expression a mix of amusement and intrigue. You rubbed your arm absentmindedly and kept your gaze downwards, attempting to will away the blush that had made itself home on your face.

He must have a horrible impression of you now if he didn’t already… But what does that matter? You were here for answers damnit! Who cares what the ex-royal scientist thought of you? You were a monster on a mission! A mission you couldn’t fail!

Your heart filled with perseverance and you steeled your nerves, looking at Gaster straight in the eyes and preparing your demands. They died in your throat however, as you took in how he continued to stare at you, amusement overtaking his expression completely with signs of laughter dancing below the surface of the lights in his eyes.

“I said that aloud didn’t I?”

A nod of his head had you putting your face in your hands in shame, your entire face burning in embarrassment.

“I’m so sorry! ….You don’t even speak in the same language I do anyways… How would I understand you if you answered?”

Gentle fingers brushed your bangs away from your forehead and lightly tapped the center, a sudden flash of purple light erupting between you two. You lifted your head slowly, eyeing Gaster in confusion and wonder. It was as if someone had unlocked a door in your mind, as if everything that had been kept behind it now danced and somersaulted throughout your body. You felt your magic pulse in your veins. It had never been this strong…you had never felt it like this.

“What did you do?”

Gaster appeared to be proud of himself, his grin widening as he folded his hands neatly in front of him.

 

**You were blocking the flow of your magic, my dear.**

 

You jumped, yelping at the sudden deep, male voice reverberating in your ears. Was that..? Him..?

 

“U-uhm…D-doc?”

 

**Yes?**

Immediately, you reeled backwards, clutching at your head in surprise. “I CAN UNDERSTAND YOU?!”

 

**So it seems…I had to do the same thing to your father once. It’s the consequence of a buildup of negative emotions. Humans tend to work that way, I presume.**

 

“H-he stopped understanding you?”

 

**No. His magic declined in strength due to his constant worry and anxiety. Understanding me requires only the simplest of magic. You either lacked the aptitude or your magic was blocked. Since you are your father’s daughter, I assumed your problem was the latter.**

“O-oh…” That makes sense. For years, you felt almost every negative emotion under the sun. (Well, in this case, under the ground.) The hurt of your father leaving you, the despair of your mother dying, the constant anxiety you felt everyday that someone will find out about you. That must have been why it was increasingly difficult for you to learn spells beyond telekinesis and invisibility, and even though you were proficient with the spells you did know, you would have been helpless if it came down to a confrontation. But you weren’t powerless. Not anymore.

“Hey, doc-“ He rose a skeletal hand abruptly, your question dissipating on your tongue.

 

**You’ve been here too long. I advise going back, before something unfortunate happens.**

What?! But you still had so many questions to ask! You came here for answers and you had barely gotten any! You couldn’t go back now, you had to kno-

 

**I will answer your questions the next time you return, which will be easier I can assure you.**

You said that aloud again didn’t you?

 

Feeling that familiar sensation of being yanked backwards again, you caught a glimpse of Gaster turning away and disappearing before you woke up in your own bed. A sudden wave of nausea hit you, and you immediately shot up, hands clasped over your mouth as you ran to the bathroom, nearly tripping over a stack of laundry. You kneeled over the toilet for several minutes, emptying the contents of your stomach until all you could do was dry heave. Moaning as another wave of nausea crashed down, you decided to try to keep your Void trips short.

 

***

 

The next two months were dedicated to going back and forth to the Void, asking him questions about anything that happened to cross your mind. Though most of the time, they were just excuses to be in his company for a few minutes more. You briefly wondered when Gaster had wormed himself into your heart, but you attested that to the fact that you’ve been alone for far too long so naturally, you’d cling to the first person you crossed paths with. It definitely had nothing to do with his smooth, baritone voice in your head or the endearments he used when referring to you. And definitely not how your heart skipped a beat when you managed to amuse him with your antics. You shook your head, smiling a little. You couldn’t remember the last time you had a friend, but you were happy to have found one in Gaster. Although you were sure he only regarded you as his missing colleague’s daughter and probably felt obligated to answer most of your questions, he must at least appreciate your company. He had to, being stuck in the Void for so long seemed awfully lonely after all.

You pulled a knit cap over your head, your long rabbit ears sliding easily through the two holes on top. Grabbing a turtleneck sweater and slipping it on, a fluffy tail comfortably poking through the hole you had made in the back, you made your way to the front of your house, anxiety increasing with every step. Before you met Gaster, all you had wanted to do in this life was to find your father. And although you still wanted that above all else, you also wanted to help Gaster. Not only could he possibly locate your father’s whereabouts, but he was your friend now. There was no way you’d leave him in the Void, your heart wouldn’t allow it. Breathing deeply to calm your nerves, you recalled the conversation you had about it a few days ago.

_“Do you remember the first time we met?”_

 

**_Of course, my dear. The first living creature I’ve seen in years, how could I forget?_ **

 

_“Why did it look like you were ready to take my soul?”_

He had visibly stiffened, and had seemed to be contemplating whether or not he should tell you. After a few moments he had sighed.

 

**_Your father was trying to free me from the moment I ended up here. The only way to do so, however, is to bring me a powerful soul. Just like the barrier that keeps all monsterkind trapped in the Underground, it is a barrier that keeps me trapped here._ **

 

You felt your face twist into confusion. _“But that would mean…you’d need a human soul to get out!”_

 

**_Yes. Your father was ready to give me his._ **

 

Shock, disbelief, and hurt flashed through you as your felt your heart give a painful squeeze. Gaster noticed your discomfort and quickly continued.

 

**_But I refused. So he set out to find an equal substitute._**

 

_“So…when I appeared…you thought…?”_

 

**_I thought that he had succeeded. Unfortunately, it wasn’t the case._ **

****

When you had denied your soul being powerful, Gaster only shook his head, and said you were more powerful than you knew.

 

Closing your eyes you rose one arm and let it fall, hand bent towards you with fingers poised loosely. Feeling a light sheet of magic enveloping your body, you released the breath you didn’t know you were holding and reached out to open the door. You were quickly met with a blast of frozen air which caused you to shiver involuntarily. Is it just you, or was it unusually colder out today? Shrugging, you pulled your turtleneck up to cover the lower half of your face and trudged forward. Maybe it was just you. Shuddering as you placed a foot-paw in the snow, you muttered a short incantation, making sure to cover your tracks. It wouldn’t be easy, finding a substitute soul that was powerful enough to free Gaster, but you had to try. The lab in the Hotlands could yield results, so you decided to check there to start. But before actually setting off, it would probably be best if you got a few snacks…


End file.
